Field of the Invention
The present invention relates to a display control apparatus and a display control method for medical images, an image display apparatus using the display control apparatus, and a program.
Description of the Related Art
In the medical field, medical image capturing apparatuses such as X-ray computed tomography (CT) apparatuses, magnetic resonance imaging (MRI) apparatuses, and positron emission tomography (PET) apparatuses are used to capture medical images. Medical image data obtained by capturing images is subjected to various types of image processing, and stored for a certain period of time in data servers in hospitals. When making diagnoses with images, doctors use a medical image display apparatus (sometimes referred to as a viewer) to search for target medical image data and display it on a monitor, while using various functions of the medical image display apparatus.
This sort of medical image display apparatus displays a thumbnail image (hereinafter, referred to as a thumbnail) corresponding to a medical image, and, upon accepting selection of the thumbnail by a user, displays the medical image corresponding to the selected thumbnail so that a diagnosis can be made from the medical image. The displayed medical image from which a diagnosis is to be made can be subjected to various functions of the medical image display apparatus, such as an enlargement and reduction function, a density value conversion function, a display position parallel movement function, a graphic drawing function, and a density value measurement function, on the entire image.
Meanwhile, medical image data has different optimum display conditions depending on anatomically classified areas (anatomical areas) even if they are areas displayed in the same image, and, thus, the images are displayed with their display condition being changed by a user according to an area that is to be observed, and are subjected to interpretation. For example, the user can change the display condition, using a known density value conversion function in the medical image display apparatus. The density value conversion function is a function of converting each pixel value in the gray scale according to a predetermined rule. Typically, a CT image is expressed in a Hounsfield unit (HU) value in 12-bit tones (4,096 tones) per pixel, and this HU value is stored as a pixel value. When a doctor observes a CT image, two density conversion parameters consisting of window level (WL) and window width (WW) as defined in the DICOM standard are used to convert a 12-bit tone pixel value (HU value) into an 8-bit tone value, and the image is displayed on a display screen. Accordingly, it is possible to easily see a difference in HU values (density difference) in a specific organ or tissue. Also in images (MRI images, PET images, ultrasonic images, etc.) other than CT images, density conversion as described above is performed in order to make it possible to easily see a difference in pixel values (density difference). More specifically, when observing in detail a lung-field region in a CT image showing a breast region, the WL is set to −600, and the WW is set to 1500. When observing in detail a mediastinal region in a CT image showing a breast region, the WL is set to 60, and the WW is set to 400. When observing in detail a bone region in a CT image showing a breast region, the WL is set to 500, and the WW is set to 2500.
Japanese Patent Laid-Open No. 2011-217947 (hereinafter, referred to as Document 1) describes a technique in which, when a freely selected area is designated in three-dimensional data, an image display condition is changed. With this technique, a CT image can be efficiently displayed in a display condition corresponding to a designated area, and, thus, the user effort can be reduced.
However, typically, a thumbnail is merely for specifying a corresponding medical image, and, thus, after a medical image corresponding to a selected thumbnail is displayed, the display condition has to be changed using the technique as shown in Document 1. Accordingly, there is a problem that it requires effort to perform interpretation.